Our major accomplishments are in the following areas:[unreadable] [unreadable] 1) Inner ear analyses of Noggin knockout mouse embryos (manuscript published)[unreadable] [unreadable] Mutations of the NOGGIN gene in humans are associated with several autosomal dominant disorders such as symphalangism and multiple synotoses. These syndromes are characterized by skeletal defects and synotoses, which include conductive hearing loss. Noggin encodes a protein that antagonizes activities of Bone morphogenetic proteins (BMP). To understand the role of Noggin in ear development, we analyzed the ear phenotypes of Noggin homozygous mice. We published a paper this year describing the inner ears of Noggin knockout embryos. We show that the inner ear phenotypes observed in Noggin knockout embryos are largely due to a misalignment of the otocysts with the hindbrain during early embryogenesis. We propose that this misalignment disrupted the normal hindbrain signaling that is required for proper inner ear morphogenesis. We tested this hypothesis by generating similar misalignment in chicken embryo surgically as what was observed in Noggin -/- embryos. The resulting inner ear phenotypes in chicken resemble those in Noggin mutants, in particularly the saccule and cochlear duct malformations. These results indicate that the inner ear phenotypes observed in Noggin mutants are largely attributed to improper formation of the body axis.[unreadable] [unreadable] 2) Noggin heterozygous mice an animal model for conductive hearing loss (manuscript submitted)[unreadable] [unreadable] We conducted a study in the Noggin heterozygous mice. We show that the Noggin heterozygous mice suffer from conductive hearing loss, similar to the human patients with NOGGIN mutations. Since Noggin is a single exon gene, our results strongly suggest that the autosomal dominant disorders associated with NOGGIN mutations in humans are due to haploinsufficiency of NOGGIN.[unreadable] We discovered that the heterozygous mice with hearing loss have an ectopic bone fragment connecting one of the middle ear ossicles, the stapes, to the wall of the tympanum. This fixation most likely impedes the mobility of the stapes during sound conduction leading to hearing loss. We concluded from our analyses that the ectopic bone fragment is not due to de novo synthesis. Most likely, the extra bone formed by an incomplete separation of the prospective stapes from its precursor in the second branchial arch due to unopposed BMP activities. Since the long-term prognosis is not ideal for patients with NOGGIN mutations who underwent corrective surgery for stapes ankylosis, these Noggin mutant mice will continue to serve as a good model for exploring better strategies to alleviate hearing loss.[unreadable] [unreadable] 3) Roe of Sonic hedgehog (Shh) and Gli proteins in inner ear development (manuscript published)[unreadable] [unreadable] From the analyses of mouse mutants with various genetic combinations of mutant alleles such as Shh, Gli2, Gli3, and Gli3 delta699, we show that several mechanisms are involved in Shh signal transduction in the inner ear. The formation of the distal cochlear duct, which is positioned closest to the source of Shh in the notchord and floor plate, requires robust Gli2 and Gli3 activator functions. The proximal region of the cochlear duct requires less Shh signaling to antagonize Gli3 repressors. The dorsal vestibule of the inner ear requires little Shh signaling but Gli3 repressor is important for the formation of this region. Thus the graded Shh signaling from the ventral midline specifies various inner ear structures along the dorsal-ventral axis.